PARAMETRIC SOURCE OF ELF TRANSIENTS

ABSTRACT

We address changes in the global electric circuit, which were caused by arrival of the giant gamma flare from SGR 1806-20 to the dayside of the globe. It is shown that a parametric source of radio emission depends on the structure of the global electric circuit. We consider the formation of a discrete radio pulse in the framework of realistic exponential height profile of air resistance. We show that altitudes around the tropopause play a significant role in pulse formation. Spectral density radiated is inversely proportional to the frequency. Waveforms are computed of a parametric pulse caused by the gamma rays arrival.